The invention relates to a device for mixing, cooling, heating, drying and/or granulating of powder and/or granular materials, comprising a conical mixing vessel having a vertical axis, which narrows in a downward direction and in which at least one vertical mixing shaft can rotate, from which mixing shaft a number of elements project, of which the outer ends extend until close to the sidewall of the vessel.
From U.S. Pat. No. 5,344,232 a medical mixer of very small dimensions is known for preparing under partial vacuum small quantities of bone cement for orthopedic purposes in or near the operating room. This cement is used during medical bone operations, in which a prosthesis is fastened to a bone, such as for instance a hip. The shelf life of this bone cement is very limited, so that it is prepared shortly before use.
The mixer comprises a hand driven vertical mixing shaft, which extends through a flat upper lid and carries two opposite mixing paddles with different height. At a low number of revolutions, of for instance 30 to 40 revolutions per minute, a liquid monomer is mixed with a solid polymer powder under partial vacuum to a paste, which is pressed into a cartridge that is connected to a lower lid of the mixer and is thus ready for use.
The object of the invention is the further development of this mixing device to an intensive mixer for industrial use, with which powdery, granular and/or pasty materials can be mixed, cooled, heated, dried and/or granulated.
According to the invention this object is reached in that the mixing shaft carries a great number of elements, and has a high to very high number of revolutions, by which the material to be treated experiences a very strong shearing on both the elements and the inner wall, the one and the other such, that in a very short time, a very intensive mixing of the product is effected.
According to a main embodiment of the invention the number of revolutions of the mixing shaft comprises 100 to 1000 revolutions per minute.
In a first preferential embodiment of the invention, in which the elements each carry one or more mixing paddles at the other end, that extend with another end parallel to and near to the inner sidewall of the vessel, the elements are rod shaped and have a large radial dimension, whereas the paddles are plate shaped and have a small radial dimension and are limited rotatable over an angle around the longitudinal axis of the rod shaped element.
In a second preferential embodiment of the invention the elements comprise knives, of which at least a part has a variable angle position with the vertical. Other characteristics and advantages of the invention will be apparent from the description below of a number of embodiments, referring to the accompanying drawings wherein like numerals depict like parts, and wherein: